The present invention relates in general to molten metal casting of engine components such as cylinder blocks and cylinder heads, and, more specifically, to a process and casting core for improving the structure of a water jacket (i.e., cooling passage) to improve heat flow and mechanical strength.
Cylinder blocks and cylinder heads are examples of engine components for internal combustion engines that are typically manufactured by casting an aluminum alloy in a mold made from hardened sand cores. Water jackets (i.e., cooling passages) formed in cylinder blocks and heads using existing casting methods result in a forced compromise between efficiency of heat transfer and the structural support and rigidity of the cast part. Water jackets provide a method of heat transfer from engine components to the cooling system. To efficiently move heat from the engine itself into the coolant flowing in the water jacket, the water jacket is separated from the heat source by only a thin wall of the cast metal. However, thin sections of minimally supported material exhibit reduced strength to react against mechanical and combustion loads. Due to the lack of support, the load carrying ability of the structure in the vicinity of the water jacket can be significantly affected by small changes in material wall thickness between the water jacket cavity and the cylinder or combustion chamber. The structural requirements due to the lack of structure in the areas of the water jacket may necessitate more material thickness/volume to provide structural performance even though less material thickness would provide for better heat transfer and cooling.
It would be desirable to reduce wall thickness for better cooling efficiency while maintaining wall strength for better mechanical performance.